1. Field of the Invention
The present invention generally relates to motors, and more particularly, to gear engagement mechanisms for motors.
2. Description of the Related Art
Starter motors for internal combustion engines are designed to engage a pinion gear, a first rotatable element, with a flywheel gear, a second rotatable element. When engaged and power is applied to the starter motor, the flywheel is turned to start the engine. The conventional starter motor comprises a hold-in winding 1, a pull-in winding 2, a return spring 3, an engaging lever 4, a meshing spring 5, a driver 6, a roller-type overrunning clutch 7, a pinion 8, an armature shaft 9, a stop ring 10, a spiral spline 11, a guide ring 12, a terminal 13, a contact 14, a contact break spring 15, a moving contact 16, a solenoid switch 17, a commutator end shield 18, a brush holder 19, a carbon brush 20, a commutator 21, a pole shoe 22, an armature 23, a field frame 24, and an excitation winding 25. The arrangement and assembly of these components is well known in the art.
Conventional starter motors, for example as depicted in FIG. 1, typically require a starter assembly to be placed offset/behind the flywheel, taking up valuable envelope space in the engine. The current design further requires a heavy starter, thereby affecting vehicle's fuel economy. More importantly however, the present designs require the drive gear to advance axially forward and engage the flywheel before the starter turns. The advancement of the drive gear requires that the armature shaft be journaled on a nose casting, adding weight and complexity; requires expensive heat treat and helicoidal lamination of the armature shaft splines; requires a large solenoid to advance and hold the large mass of the drive gear; and requires a more complex offset lever system.
The large solenoid required to advance and hold the large mass of the drive gear needs extensive copper coils (2 of them) adding mass and cost. Moreover, the extensive coils require more amp draw from the electrical system, and more power wasted in order to have the starter perform its function. The large solenoid requires complex design with expensive terminals and contacts which tent to weld and wear over time. In addition, the solenoid phenolic caps tend to crack and break due to handling or thermal issues. The large solenoid design further leads to moisture accumulation and contact freezing, leading to a non-starting (click-no-crank) condition. Also, coil gassing creates deposits on the contacts, leading to electrical insulation deterioration and non-function of the starter system.
In addition, the drive gear advance results in frequent impacts with the flywheel, leading to both drive gear and flywheel damage. Accordingly, expensive heat treatments of both components are incurred to help improve component life. Moreover, the large axial travel, time, and energy expended for starting cycle to initiate and ignite engine reduces the efficiency of the operation of the starter motor and leads to premature wear and/or failure of the starter motor.
Therefore, there is a need in the art for an improved starter motor.